It is generally agreed that a relationship exists between intraocular pressure (IOP) and damage caused to the eye. It has long been known that the IOP displays a daily variation that differs from person to person and even from day to day. It has been repeatedly stated, therefore, that the assessment of the IOP and its variations is important in the diagnosis of glaucoma and its treatment, which is mainly directed toward normalizing the pressure. It is the opinion of many opthalmologists that home tonometry, namely, the measurement of the IOP at the patient's home, can be very valuable. However, because no proper instrument is available this procedure has not been widely utilized. We have developed a self tonometer that is used by the patient at home and work. It has been shown that patients obtain results with a reproducibility comparable to that of tonometers used in the clinic. The preliminary clinical results show that in a significant number of cases the highest IOP would not have been detected during regular office hours. Moreover, large IOP variations were noticed even in apparently controlled patients. The first objective of this proposal is to measure the mean IOP, IOP variation, and IOP peaks in two control groups: normals and well-controlled glaucoma patients. These results will then be used in the diagnosis of patients who could benefit immediately from the data: those with "low tension" and those with uncontrolled glaucoma. Detection of IOP peaks in these patients would alter the diagnosis and provide a rationale for increasing their therapy. The main effort, however, is to assess the value of home tonometry in identifying individuals at risk (1) of developing glaucoma among ocular hypertensive patients, and (2) of further losing visual field among glaucoma patients. We will follow up subjects with large peaks or variations in IOP and compare their progression to that of control groups with normal IOP characteristics.